U.S. patent number 4,022,715 [Application Number 05/645,579] was granted by the patent office on 1977-05-10 for process for catalyst materials of increased pore volume and pore diameter.
This patent grant is currently assigned to American Cyanamid Company. Invention is credited to Robert Alan Bornfriend.
United States Patent |
4,022,715 |
Bornfriend |
May 10, 1977 |
Process for catalyst materials of increased pore volume and pore
diameter
Abstract
Disclosed is a process for producing molded catalyst materials
of increased pore volume and pore diameter which comprises
incorporating a blowing agent in the composition from which they
are molded.
Inventors: |
Bornfriend; Robert Alan
(Ridgefield, CT) |
Assignee: |
American Cyanamid Company
(Stamford, CT)
|
Family
ID: |
24589584 |
Appl.
No.: |
05/645,579 |
Filed: |
December 31, 1975 |
Current U.S.
Class: |
502/439 |
Current CPC
Class: |
B01J
37/0018 (20130101) |
Current International
Class: |
B01J
37/00 (20060101); B01J 021/04 () |
Field of
Search: |
;252/463,455R,477R,449
;106/87 ;423/628,631 ;264/44,59 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3591394 |
July 1971 |
Diggelmann et al. |
3608060 |
September 1971 |
Osment et al. |
3907512 |
September 1975 |
Ziegenhain et al. |
|
Primary Examiner: Shine; W. J.
Attorney, Agent or Firm: Van Loo; William J.
Claims
We claim:
1. A process for producing a molded catalyst material of increased
porosity which comprises: (1) preparing a moldable aqueous
dispersion of an inorganic oxide gel; (2) uniformly incorporating
in said dispersion an effective amount of a compound which
undergoes decomposition with the liberation of gas at a
decomposition temperature above the boiling point of water at
atmospheric pressure; (3) molding the resultant composition to form
a desired structure; and (4) thereafter heating said structure to a
temperature above said decomposition temperature so as to liberate
said gas while setting the structure formed.
2. The process of claim 1 wherein said heating is carried out in
more than one step.
3. The process of claim 2 wherein one of said heating steps is a
calcination step.
4. The process of claim 1 wherein said decomposable compound is
p,p'-oxybis(benzene sulfonyl hydrazide).
5. The process of claim 1 wherein said decomposable compound is
toluene sulfonyl hydrazide.
6. The process of claim 1 wherein said inorganic oxide gel is
alumina.
7. The process of claim 1 wherein said molding is accomplished by
extruding.
8. The process of claim 1 wherein the decomposable compound is
incorporated as an emulsion in said aqueous medium.
9. The process of claim 2 wherein said structure if heated at
250.degree.-400.degree. F. in one step followed by calcination at
800.degree.-1300.degree. F.
Description
This invention relates to a process for providing a catalyst
support of increased porosity. More particularly, this invention
relates to such a process wherein by incorporation in the
composition from which the support is molded a compound which
decomposes at elevated temperature to gaseous products and
subsequent exposure to said elevated temperature, increased
porosity results.
Inorganic oxide gels are widely used in the preparation of catalyst
materials. A particularly desirable type of catalyst material is
one in which the inorganic oxide gel is molded into a suitable
support form, such as a small cylinder. Such supports may be active
catalysts as prepared or may require promotion and/or activation by
subsequent treatment.
A conventional process for preparing molded catalysts or catalyst
supports consists of preparing a moldable composition of suitable
inorganic oxide gel, molding the resultant composition into the
desired structure, and thereafter setting the resultant structure
by heat treatment. While this procedure provides desirable
catalysts or catalyst supports for many purposes, the resultant
catalyst materials are generally characterized by limited pore
volume and by pores of limited diameter. As a result, these
catalysts are limited in activity and are not suitably effective in
reactions involving large molecules.
Numerous processes have been suggested in the past to provide
molded catalysts of increased porosity and pore diameter. One such
process involves incorporation of a volatile liquid in the molding
composition, which liquid is volatilized after support molding.
However, such process provides only limited increases in porosity
and pore diameter. Another process incorporates within the molded
structure synthetic or natural fibers which are subsequently burned
off to provide voids. However, it is difficult to affect complete
burn-off and catalyst poisons remain. Still another process
involves leaching the heat-set support structure to dissolve out
portions of the support composition. However, such procedure
provides only limited increases in porosity before other desirable
properties such as strength, attrition resistance, and the like are
adversely affected. Still other processes have been suggested, but
all suffer from one or more deficiencies.
There continues to exist, therefore, a need for a process for
increasing the porosity and pore diameter of molded catalyst
material while overcoming deficiencies of the prior art processes.
Such a development would fill a long-felt need in the art and
provide a notable advance in the art.
In accordance with the present invention, there is provided a
process for producing a molded catalyst material of increased
porosity which comprises: (1) preparing a moldable aqueous
dispersion of an inorganic oxide gel; (2) uniformly incorporating
in said dispersion an effective amount of a compound which
undergoes decomposition with the liberation of gas at a
decomposition temperature above the boiling point of water at
atmospheric pressure; (3) molding the resultant composition to form
a desired structure; and (4) thereafter heating said structure to a
temperature above said decomposition so as to liberate said gas
while setting the structure formed.
The present invention provides catalyst materials having increased
porosity while maintaining desirable physical properties and
avoiding other deficiencies of prior art procedures. The increased
porosity is reflected in an increased proportion of pores of large
diameter. This result is surprising in view of the fact that the
decomposable compound liberates a gas.
Inorganic oxide gels useful in the process of the present invention
include alumina, silica, titania, vanadia, molybdenia and the like
as well as mixtures thereof. In addition coated gels or co-gels may
be employed such as alumina-coated silica gels, silica-coated
alumina gels and gel matrices into which are incorporated zeolites.
Suitable gels may be used as hydrogels or xerogels. The various
gels are prepared according to conventional methods.
The inorganic oxide gel is slurried in an aqueous medium to provide
a moldable composition in accordance with conventional procedures.
If desired, provision may be made for activator and/or promoter
incorporation in the moldable composition or such provision may be
deferred until the molded structure has been set and made by
typical impregnation techniques. Provisions for extrusion aids will
follow conventional procedures.
In accordance with the present invention, a compound which
decomposes with the liberation of gas is incorporated in the
moldable composition. In other applications, such decomposable
compounds are known as "blowing agents" and any of the known
blowing agents may be used provided that they decompose above the
boiling point of water at atmospheric pressure. Particularly good
results are obtained with sulfonyl hydrazides, i.e. compounds which
feature the structure ##STR1## wherein n is 1 or 2, R is lower
alkyl (C.sub.1 -C.sub.4) when n is 1, and R is --O-- when n is 2.
The preferred blowing agent is p,p'-oxybis(benzene sulfonyl
hydrazide).
Incorporation of the blowing agent may be by any convenient means
and should be uniformly dispersed. The blowing agent may be
incorporated in the moldable composition as prepared, may be
pre-dispersed in the aqueous medium, may be blended with the
inorganic oxide gel, or may be incorporated in any manner that
provides uniformity in the moldable composition.
The amount of blowing agent to be used is that which is effective
in providing the desired increase in porosity. The actual amount
will vary widely depending upon the extent to which porosity
increases are desired, the nature of the inorganic oxide gel being
processed, and the procedure of molding followed. Generally, an
increase will be obtained with usage as low as 0.05 weight percent
of blowing agent based on the dry weight of the gel being
processed. Particularly good results are obtained at usage levels
in the range of about 0.25 to 0.5%, same basis. The upper limit
appears to be limited only by practical considerations.
After the moldable composition with its incorporated content of
blowing agent is suitable for processing, it is molded to provide
the desired structure. Molding is preferably carried out by
extrusion in accordance with conventional procedures. Other methods
such as pilling, pelletizing, and the like may be employed. The
preferred structures are those of cylinders of 1/8 and 1/16 inch
diameters. Polylobal cross-sectional shapes are also preferred for
certain applications.
After the molded structure is obtained, it is exposed to heat
treatment above the decomposition temperature of the decomposable
compound so as to set the structure while the decomposition gases
are being liberated. The particular nature of the heat treatment is
not particularly critical so long as the temperature requirements
are met. Generally the molded structure are subjected to a
preliminary mild heat treatment and subsequently calcined, but the
mild treatment may be eliminated. In the latter instance, the
molded structure will gradually reach the calcination temperature
and pass through the decomposition temperature of the blowing agent
en route. The mild heat treatment and/or calcination are carried
out in accordance with conventional procedures. When mild heat
treatment is carried out it may be in the range of about
250.degree. - 400.degree. F. for from about 1 to 18 hours.
Calcination temperatures are generally in the range of 800.degree.
- 1300.degree. F. and the time of calcination is generally an hour
or more. It is immaterial whether or not the decomposable compound
decomposes under the optional mild heat treatment or when exposed
to calcination.
A "catalyst material", as that term is used herein, refers to a
support, which may be active in certain reactions, as well as
promoted and/or activated supports. The molded structure,
therefore, after calcination may be used directly as a catalyst if
it is active or provision for promotion and/or activation were made
in the moldable composition. In other cases, the molded structure
is promoted and/or activated in accordance with conventional
procedures.
The molded catalyst materials provided by the process of the
present invention, as indicated, are characterized by increased
porosity and a larger proportion of pores of large diameter than
molded catalyst materials made from the same inorganic oxide gels
according to conventional processes. It is known that increased
porosity and pore diameter provide improved catalysts in numerous
catalytic reactions. It is also known that catalysts having
increased pore diameter have utility in reactions involving large
molecules which are not effectively catalyzed by catalysts of
smaller pore diameter. It is readily apparent, therefore, that
molded catalyst materials provided by the process of the present
invention has advantages in particular reactions over molded
catalyst materials provided by conventional processes.
The invention is further illustrated in the examples which follow.
In the following examples, reference is made to physical properties
such as pore volume and the like. These tests are determined in
accordance with the procedures described in the booklet "Test
Methods For Synthetic Fluid Cracking Catalysts", published by
American Cyanamid Company, January 1957, and widely distributed in
the field. An additional test not given in this booklet is Crush
Strength. This value is determined by placing a molded structure on
its side between two parallel plates. Force is applied to the top
plate by means of pneumatic pressure until the structure is
crushed. The device is such that the air pressure in pounds to
cause crushing is the Crush Strength of the structure.
EXAMPLE 1
25 Grams of p,p'-oxybis(benzene sulfonyl hydrazide) were dissolved
in 250 ml. of acetone, and the solution was added to 15 lbs. of
deionized water. This water emulsion was added to 14 lbs. of
precipitated alumina powder in a Lancaster mix muller, along with
2.5 lbs. of aqueous ammonia (28% NH.sub.3), and 52 gms of
polyacrylamide extrusion aid. The mix was mulled for 25 minutes,
after which two more pounds of precipitated alumina powder was
added. After 15 more minutes, the mix was extruded through a 1/16
inch die plate. The mix pH was 9.8 and solids were 35%.
The raw extrudates were loaded onto trays and charged to an oven
preheated to 350.degree. F. After drying overnight, the extrudates
were calcined for an hour at 1100.degree. F. Properties of this
sample are compared in the table below with those properties of a
standard precipitated alumina extrudate made without the blowing
agent included.
TABLE A
__________________________________________________________________________
Porosity (cc/g) in Pore Sizes Compacted Pore Bulk Particle Crush
Volume 35A .degree. - 150A 150A.degree. - 1.77 Density Diameter
Strength Sample cc/g dia. .mu.dia. g/cc (inches) (lbs.)
__________________________________________________________________________
Product from .88 .592 .225 .54 .059 12 Example 1 Control .675 .558
.044 .67 .061 13 (without blowing agent)
__________________________________________________________________________
EXAMPLE 2
20 Gms of blowing agent were dissolved in about 200 ml. of acetone
and the solution was added to 10 lbs. of deionized water. This
water emulsion was added to 13 lbs. of a precipitated alumina
powder in a muller, and mulled for 30 minutes. The mix was extruded
through a 1/16 inch die plate. The mix solids were about 39%. The
raw extrudates then were loaded on to trays and charged to an oven
preheated to 350.degree. F. After drying overnight, the extrudates
were calcined for an hour at 1100.degree. F. Properties for
extrudates made with two different blowing agents and a combination
thereof are shown in the table below:
TABLE B ______________________________________ Pore Volume Sample
Blowing Agent (cc/g) ______________________________________ 1
p,p'-oxybis (benzene .902 sulfonyl hydrazide) 2 toluene sulfonyl
.765 hydrazide 3 50 - 50 mixture of .698 agents 1 and 2 control
None .573 ______________________________________
* * * * *